This invention relates to a pressure regulation valve of the type useable in an aircraft environmental control system. More particularly, it relates to the valve used in the European Airbus.
Two pneumatic valves are typically linked, in a series, to control the flow in an environmental control system ("ECS"). The first is called a pressure regulation valve ("PRY") and it maintains a constant pressure downstream of the valve regardless of upstream conditions. The second is a control valve that modifies the system flow, using the discharge pressure of the PRV as a reference signal.
The present PRV is designed for use in an ECS, such as the cargo heating system for the European Airbus A320. That heating system is manufactured, as Model No. EC100, by Hamilton Standard, a division of United Technologies Corporation, the Assignee of this invention. Such an ECS may be used in conjunction with a gas-turbine engine, such as Model No. V2500, provided by Pratt & Whitney, also a division of United Technologies Corporation. That engine is implemented on the Airbus.
In the European Airbus, the PRV consists of a butterfly valve, actuator and controller. The valve has a main body through which the fluid flows and a disk that pivots to selectively choke or block the flow, thus controlling the pressure. A pressure tap downstream of the valve is used to sense the pressure. The controller uses this signal to maintain a constant pressure, downstream of the disk, regardless of changes in upstream flow or pressure.
Because of its blocking nature, the butterfly disk imparts a swirl to the flow that passes over it. That creates turbulence and cavitation. Textbooks on fluidics therefore suggest that the downstream pressure tap for control valve testing be located four to six pipe diameters downstream from the outlet connection of the butterfly valve being tested. This allows the flow to return to normal (i.e., become more laminar), sufficient to take an accurate reading of its static pressure.
This is fine in theory; but it creates design problems in an ECS for the Airbus, such as the aforementioned cargo heating system. To correctly monitor the downstream pressure from the PRV in that heating system, this guideline suggests that piping and an extra sensing line (routed back to the PRV) be located beyond the valve's main body. This extra plumbing complicates the valve's installation in the aircraft. For example, the sensing line must be clamped to aircraft structure to protect the line from vibration. It also increases the time required to remove and replace the valve and also adds extra weight. Where compactness and reduction in weight are critical goals in the Airbus (as in all flight systems), it would be beneficial if this extra hardware could be deleted there without sacrificing any appreciable accuracy in the pressure reading.
Accordingly, it is a principal object of the present invention to provide an improved pressure regulation valve, with an integrated downstream pressure tap, that overcomes the deficiencies of the prior art.
It is another general object to provide a unique baffle insert that enables an accurate pressure tap to be located within the valve body rather than downstream.
It is a specific object to provide an improved pressure regulation valve that eliminates plumbing a separate line four to six pipe diameters downstream.
It is another object to provide a baffle insert that fits into a standard channel of the cargo heating system for the Airbus A320.